Power tool and control method of the same

ABSTRACT

A power tool has a functional component, a motor, a power supply module, a controller and a drive circuit including a first drive terminal and a second drive terminal respectively electrically connected to a first power terminal and a second power terminal of the power supply module, multiple high-side switches wherein high-side terminals of the high-side switches are respectively electrically connected to the first drive terminal, and multiple low-side switches wherein low-side terminals of the low-side switches are respectively electrically connected to the second drive terminal. The controller is configured to output a first control signal to one high-side switch to place it in an on or off state and output a second control signal to one low-side switch to place it in the other state. The low-side terminal of one high-side switch is connected to the high-side terminal of one low-side switch.

RELATED APPLICATION INFORMATION

The present application is a continuation of U.S. application Ser. No.17/080,978, filed on Oct. 27, 2020, which application is a continuationof International Application Number PCT/CN2019/083863, filed on Apr. 23,2019, the disclosure of which is incorporated herein by reference in itsentirety. Further, this application claims the priority of ChinesePatent Application No. 201810413922.3, filed on May 3, 2018 in the SIPO(State Intellectual Property Office—Chinese Patent Office), thedisclosure of which is incorporated herein in their entirety byreference.

FIELD

The present disclosure relates to a power tool and a control methodthereof, in particular to a power tool and a control method thereof thatcan suppress the temperature rise and power loss of switches.

BACKGROUND

Power tools generally use motors to drive a functional component tomove, so as to realize the functions of power tools. The motor may be abrushless motor or a brushed motor. For brushless motors, the drivecircuit is generally controlled by an inverter drive bridge circuit. Thepower components of the inverter drive bridge circuit, that is, theswitches (MOSFETs, IGBTs, etc.) generally generate a lot of heat.Switches have parasitic diodes; when a switch is toggled from the onstate to the off state, the current in the motor windings will passthrough the parasitic diode of another switch because current is nottransient. The parasitic diode heats up due to the internal resistance,rising the temperature of the switch of the parasitic diode and thedrive circuit. Especially, under heavy load and high current, the heatloss is more significant.

SUMMARY

In order to cure the deficiencies of the prior art, the purpose of thepresent disclosure is to provide a power tool and a control methodthereof that can suppress the temperature rise and power loss ofswitches.

In order to achieve the above objectives, the present disclosure adoptsthe following technical solutions:

An example power tool includes: a functional component for realizing afunction of the power tool; a motor for driving the functionalcomponent, the motor having a plurality of windings; a power supplymodule configured to provide power supply current, the power supplymodule including a first power terminal and a second power terminal; adrive circuit electrically connected to the motor, the drive circuitincluding: a first drive terminal electrically connected with the firstpower terminal; a second drive terminal electrically connected with thesecond power terminal; a plurality of high-side switches, high-sideterminals of the plurality of high-side switches being respectivelyelectrically connected to the first drive terminal; a plurality oflow-side switches, low-side terminals of the plurality of low-sideswitches being respectively electrically connected to the second driveterminal; and a controller configured to: output a first control signalto one of the plurality of high-side switches to make one of theplurality of high-side switches in an on state or an off state; andoutput a second control signal to one of the plurality of low-sideswitches to make one of the plurality of low-side switches in the otherof the on state and the off state; wherein the low-side terminal of oneof the plurality of high-side switches is connected to the high-sideterminal of one of the plurality of low-side switches.

Optionally, the first control signal output by the controller is a firstPWM signal and the second control signal output by the controller is asecond PWM signal.

Optionally, a duty cycle of the first PWM signal ranges from 20% to 90%.

Optionally, a duty cycle of the first PWM signal ranges from 10% to 95%.

Optionally, a duty cycle of the first PWM signal ranges from 30% to 95%.

Optionally, an interval between a falling edge of the first controlsignal and a rising edge of the second control signal is a first presetduration.

Optionally, a value range of the first preset duration is 5 microsecondsto 10 microseconds.

Optionally, an interval between a rising edge of the first controlsignal and a falling edge of the second control signal is a secondpreset duration.

Optionally, a value range of the second preset duration is 5microseconds to 30 microseconds.

Optionally, an interval between a falling edge of the first controlsignal and a rising edge of the second control signal is a first presetduration, and an interval between a rising edge of the first controlsignal and a falling edge of the second control signal is a secondpreset duration.

Optionally, a ratio of the first preset duration to the second presetduration is less than or equal to 1.

Optionally, the controller outputs the first control signal and thesecond control signal synchronously.

Optionally, a sum of a duty cycle of the first PWM signal and a dutycycle of the second PWM signal is less than 100%.

Optionally, a duty cycle of the second PWM signal ranges from 20% to90%.

Optionally, a duty cycle of the second PWM signal ranges from 10% to95%.

Optionally, a duty cycle of the second PWM signal ranges from 30% to95%.

Optionally, the power tool further includes: a current measuring moduleconfigured to detect or estimate phase current; the controller isconfigured to: when the phase current is less than or equal to zero,output the second control signal to turn off one of the plurality oflow-side switches, or output the first control signal to control to turnoff one of the plurality of high-side switches.

Said controller may include a temperature sensor arranged inside thecontroller, and the controller estimates a temperature of the drivecircuit according to a detection value of the temperature sensor, andwhen the detection value of the temperature of the drive circuit exceedsa predetermined threshold, the controller controls the drive circuit tostop working.

Another example power tool includes: a functional component forrealizing a function of the power tool; a motor for driving thefunctional component, the motor having a plurality of windings; a powersupply module configured to provide power supply current, the powersupply module including a first power terminal and a second powerterminal; a drive circuit electrically connected to the motor, the drivecircuit including: a first drive terminal electrically connected withthe first power terminal; a second drive terminal electrically connectedwith the second power terminal; a first high-side switch, a high-sideterminal of the first high-side switch being electrically connected tothe first drive terminal; a first low-side switch, a low-side terminalof the first low-side switch being electrically connected to the seconddrive terminal; and a controller configured to: output a first controlsignal to the first high-side switch to make the first high-side switchin an on state or an off state; and output a second control signal tothe first low-side switch to make the first low-side switch is in theother of the on state and the off state; wherein the low-side terminalof the first high-side switch is connected to the high-side terminal ofthe first low-side switch.

Optionally, the drive circuit further includes a second low-side switch,and a low-side terminal of the second low-side switch is electricallyconnected to the second drive terminal; the controller is configured to:output the first control signal to the first high-side switch and thesecond low-side switch to form a first current circuitry; in the firstcurrent circuitry, the power supply current provided by the power supplymodule passes through the first drive terminal, the first high-sideswitch, the plurality of windings, the second low-side switch and thesecond drive terminal.

Optionally, the first control signal output by the controller is a firstPWM signal; the second control signal output by the controller is asecond PWM signal.

Optionally, a duty cycle of the first PWM signal ranges from 20% to 90%.

Optionally, a duty cycle of the first PWM signal ranges from 10% to 95%.

Optionally, a duty cycle of the first PWM signal ranges from 30% to 95%.

Optionally, an interval between a falling edge of the first controlsignal and a rising edge of the second control signal is a first presetduration.

Optionally, a value range of the first preset duration is 5 microsecondsto 10 microseconds.

Optionally, an interval between a rising edge of the first controlsignal and a falling edge of the second control signal is a secondpreset duration.

Optionally, an interval between a falling edge of the first controlsignal and a rising edge of the second control signal is a first presetduration, and an interval between a rising edge of the first controlsignal and a falling edge of the second control signal is a secondpreset duration.

Optionally, a ratio of the first preset duration to the second presetduration is less than or equal to 1.

Optionally, the controller outputs the first control signal and thesecond control signal synchronously.

Optionally, a sum of a duty cycle of the first PWM signal and a dutycycle of the second PWM signal is less than 100%.

Optionally, a duty cycle of the second PWM signal ranges from 20% to90%.

Optionally, a duty cycle of the second PWM signal ranges from 10% to95%.

Optionally, a duty cycle of the second PWM signal ranges from 30% to95%.

Optionally, the power tool further includes: a current measuring moduleconfigured to detect or estimate phase current; the controller isconfigured to: when the phase current is less than or equal to zero,output the second control signal to turn off one of the first low-sideswitch and the second low-side switch, or output the first controlsignal to turn off the first high-side switch.

An example control method of a power tool is also described. In thisexample, the power tool has a drive circuit that includes: a first driveterminal electrically connected to the first power terminal; a seconddrive terminal electrically connected to the second power terminal; aplurality of high-side switches, each high-side switch having ahigh-side terminal and a low-side terminal, the high-side terminals ofthe plurality of high-side switches being respectively electricallyconnected to the first drive terminal; and a plurality of low-sideswitches, each low-side switches having a high-side terminal and alow-side terminal, the low-side terminals of the plurality of low-sideswitches being respectively electrically connected to the second driveterminal, while the control method includes: making one of the pluralityof high-side switches in an on state or an off state; and making one ofthe plurality of low-side switches in the other of the on state and offstate; wherein the low-side terminal of one of the plurality ofhigh-side switches is connected to the high-side terminal of one of theplurality of low-side switches.

Optionally, the first control signal is a first PWM signal; the secondcontrol signal is a second PWM signal.

Optionally, a duty cycle of the first PWM signal ranges from 20% to 90%.

Optionally, a duty cycle of the first PWM signal ranges from 10% to 95%.

Optionally, a duty cycle of the first PWM signal ranges from 30% to 95%.

Optionally, an interval between a falling edge of the first controlsignal and a rising edge of the second control signal is a first presetduration.

Optionally, a value range of the first preset duration is 5 microsecondsto 10 microseconds.

Optionally, an interval between a rising edge of the first controlsignal and a falling edge of the second control signal is a secondpreset duration.

Optionally, an interval between a falling edge of the first controlsignal and a rising edge of the second control signal is a first presetduration, and an interval between a rising edge of the first controlsignal and a falling edge of the second control signal is a secondpreset duration.

Optionally, a ratio of the first preset duration to the second presetduration is less than or equal to 1.

Optionally, a sum of a duty cycle of the first PWM signal and a dutycycle of the second PWM signal is less than 100%.

Optionally, a duty cycle of the second PWM signal ranges from 20% to90%.

Optionally, a duty cycle of the second PWM signal ranges from 10% to95%.

Optionally, a duty cycle of the second PWM signal ranges from 30% to95%.

Optionally, when the phase current is less than or equal to zero, thesecond control signal turns off one of the plurality of low-sideswitches, or the first control signal turns off one of the plurality ofhigh-side switches.

The present disclosure is beneficial in that it can suppress thetemperature rise of the drive circuit and the switches, thereby reducingpower loss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a power tool according to an example;

FIG. 2 is a perspective view of a power tool according to anotherexample;

FIG. 3 is a perspective view of a power tool according to anotherexample;

FIG. 4 is a circuit system diagram of a power tool according to anexample;

FIG. 5 is a simplified diagram of the drive circuit in FIG. 4;

FIG. 6A is a waveform diagram of a control signal of a conventionaldrive circuit;

FIG. 6B is a waveform diagram of a control signal of anotherconventional drive circuit;

FIG. 7A is a diagram showing a current trend when a motor drive state isin the AB state;

FIG. 7B is a diagram showing the current trend when the motor drivestate in the AC state;

FIG. 8 is a diagram showing the current trend that is not transient whenthe motor drive state is switched from the AB state to the AC state;

FIG. 9 is a waveform diagram of a control signal applied to a controlterminal of each switch by a controller according to the presentdisclosure;

FIG. 10 is a waveform diagram of a first control signal and a secondcontrol signal according to an example;

FIG. 11 is a waveform diagram of the first control signal and a waveformdiagram of the second control signal according to another example;

FIG. 12A is an actual waveform diagram of the conventional controlsignal applied to the control terminal AH of the high-side switch Q1 andan actual waveform diagram of the control signal applied to the controlterminal AL of the low-side switch Q2;

FIG. 12B is a diagram showing the current trend of a short circuitcaused by the conventional control signal in FIG. 12 a;

FIG. 13A is a waveform diagram of current I1 of the windings under heavyload and current I2 of the windings under light load;

FIG. 13B is a diagram showing the relationship between the first controlsignal applied to the control terminal AH of the high-side switch Q1 andthe second control signal applied to the control terminal AL of thelow-side switch Q2 and the output torque of the motor according to anexample; and

FIG. 13C is a diagram showing the relationship between the controlsignal applied to the control terminal AH of the high-side switch Q1 andthe control terminal AL of the low-side switch Q2 and the output torqueof the motor according to another example.

DESCRIPTION

Hereinafter, the present disclosure will be described in detail withreference to the drawings and specific examples.

A power tool of the present disclosure may be a hand-held power tool, agarden tool, a garden vehicle such as a vehicle-type lawn mower, whichis not limited herein. Power tools 10 of the present disclosure mayinclude but are not limited to the following: screwdrivers, powerdrills, wrenches, angle grinders, and other power tools that requirespeed adjustment; sanders, and other power tools that are capable topolish workpiece; reciprocating saws, circular saws, curved saws, andother power tools that are capable to cut workpiece; electric hammers,and other power tools that are capable to impact. These tools may alsobe garden tools, such as pruners, chain saws, and vehicle-type lawnmowers; in addition, these tools may also be used for other purposes,such as mixers. As long as these power tools 10 can adopt the essentialof the technical solutions disclosed below, they fall within theprotection scope of the present disclosure.

Referring to FIG. 1, a power tool 10 includes, but is not limited to: ahousing 11, a functional component 12, and a motor 13.

The housing 11 constitutes the main part of the power tool 10 and housesthe motor 13. One end of the housing 11 is also configured to mount thefunctional component 12.

The functional component 12 is configured to implement the functions ofthe power tool 10, such as grinding and cutting. As an example, thepower tool 10 shown in FIG. 1 is a hand-held power drill, and thefunctional component 12 is a drill bit. The functional component 12 isoperatively connected with the motor 13, for example, connected with themotor shaft 13 by a tool attachment shaft.

The motor 13 is configured to drive the functional component 12 so as todrive the functional component 12 to work and provide power for thefunctional component 12. Specifically, the motor 13 includes a motorshaft, a rotor, a stator, and multi-phase windings (FIGS. 4 and 5). Themotor shaft is operatively connected with the functional component 12,for example, through a transmission device 14, the motor shaft, and atool attachment shaft supporting the functional component, the drivingforce of the motor shaft is transmitted to the tool attachment shaft tomake the functional component 12 installed on the tool attachment shaftwork.

Referring to FIG. 2, as an example, a power tool 20 is a hand-heldcircular saw including a bottom plate 21, a housing 22, a blade guard23, a blade shaft 24, a motor 25, a motor shaft 251, a transmissiondevice 26, a battery pack 27, a circuit board 28 and a plurality ofelectronic components or electronic parts arranged on the circuit board28.

The bottom plate 21 includes a bottom plate plane for contact with theworkpiece, and the housing 22 is connected with the bottom plate 21 andfixed above the bottom plate plane. For circular saws, a saw blade isused as the functional component to realize the cutting function, andthe blade shaft 24 is used as the tool attachment shaft to support therotation of the saw blade inside the blade guard 23 to realize thecutting operation to the workpiece. The blade guard 23 is connected tothe housing 22.

The motor 25 is arranged inside the housing 22. The motor 25 includes astator, a rotor and multi-phase windings. The motor shaft 231 isconnected to the rotor and driven by the rotor. The motor 25 can beoperatively connected with the saw blade through the transmission device26. Specifically, the motor 25 is connected with the motor shaft 251 andthe blade shaft 24 through the transmission device 26 and transmits therotational movement of the motor shaft 251 to the blade shaft 24,thereby driving the saw blade to rotate. Among them, the battery pack 27is used as a power supply module to provide electrical energy for thepower tool 20.

Referring to FIG. 3, an impact screwdriver 30 has a similar shape to apistol, and mainly includes: a housing 31, the housing 31 having asubstantially cylindrical part a handle 32 arranged at a certain angleto the cylindrical part, and a battery 33 arranged inside the handle.The battery 33 is used as a power supply module to provide electricalenergy for the impact screwdriver 30. The handle 32 is provided with anoperation switch 34 for controlling the start of the tool, and theconnecting part of the handle 32 and the cylindrical part is alsoprovided with a reverse button 35, which is provided respectively onboth sides of the housing 31 for controlling the forward and reverserotation of the tool. There is also a circuit board inside the handle,and the circuit board integrates electronic components or electronicparts such as a drive circuit and a controller. Taking the distal end ofthe housing 31 away from the handle 32 as a front end, and the oppositeend as a rear end, a motor 36, a transmission device 37 driven by themotor, and an impact part 38 are arranged sequentially from the front tothe back. The motor 17 has a motor shaft that provides rotationaloutput, and the top of the motor shaft is provided with a motor gear fortransmitting the rotational output power of the motor 17 to thetransmission device 37 through a gear structure. The transmission device37 is configured to decelerate and then output the rotational output ofthe motor shaft. The tool attachment shaft is configured to support thetool attachment and is connected to the motor shaft through atransmission device 37.

The operation of the above power tools (10, 20, and 30) also depends oncircuit systems. Referring to FIG. 4, as an example of a power toolcircuit system 40, taking the power tool 10 as an example, the powertool 10 further includes: a power supply module 41, a controller 42, anda drive circuit 43. FIG. 4 is only an exemplary illustration and doesnot limit the content of the present disclosure.

The power supply module 41 is used to provide power to the power tool10. The power supply module 41 includes a first power terminal 41 a anda second power terminal 41 b (FIG. 5). Optionally, the first powerterminal 41 a is specifically the positive power terminal of the powersupply module 41, and the second power terminal 41 b is specifically thenegative power terminal of the power supply module 41. The power supplymodule 41 enables a potential difference to be generated between thefirst power terminal 41 a and the second power terminal 41 b. The powersupply module 41 may be electrically connected with an external powersource to provide electrical energy for the power tool 10. The externalpower source may be an AC power source or a DC power source, forexample, a battery pack. In some examples, for an AC power source, thepower supply module 41 may rectify, filter, divide, and step down the ACsignal output by the AC power source through a hardware circuit; for aDC power source, the power supply module 41 may include DC-DC conversioncircuit, etc.

In some examples, the power tool 10 further includes a controller powersupply module 47, which is electrically connected to the power supplymodule 41 and the controller 42. The controller power supply module 47is configured to convert the electrical energy supplied from the powersupply module 41 to the electrical energy consumed by the controller 42.

The controller 41 is electrically connected to the drive circuit 43 foroutputting drive signals to control the operation of the drive circuit43. In some examples, the controller 41 uses a dedicated control chip(for example, MCU, microcontroller 42, Microcontroller Unit). Thecontrol chip includes a power drive unit and the power drive unit isused to enhance the drive capability of the output signals of thecontroller 41. The power drive unit can also be implemented by anexternal power drive unit.

The drive circuit 43 is connected with the motor. The motors (13, 25)may be brushless motors 44 or brushed motors. The brushless motor 44 istaken as an example to illustrate the solution of the presentdisclosure.

The brushless motor 44 includes multi-phase windings. Alternatively, thebrushless motor 44 includes a first phase winding A, a second phasewinding B, a third phase winding C, and a drive circuit 43 for drivingthe motor 44 to work. The drive circuit 43 includes: a first driveterminal 43 a, the first drive terminal 43 a being configured toelectrically connect with the first power terminal 41 a of the powersupply module 41; and a second drive terminal 43 b, the second driveterminal 43 b being configured to electrically connect with the secondpower terminal 41 b of the power supply module 41. The drive circuit 43further includes a plurality of high-side switches, the high-sideterminals of the high-side switches being respectively electricallyconnected to the first drive terminal; and a plurality of low-sideswitches, the low-side terminals of the low-side switches beingrespectively electrically connected to the second drive terminal.

Optionally, the plurality of high-side switches are switches Q1, Q3, andQ5 in FIG. 5. Each high-side switch has a high-side terminal and alow-side terminal: the high-side switch Q1 has a high-side terminal Q1Hand a low -side terminal Q1L; the high-side switch Q3 has a high-sideterminal Q3H and a low-side terminal Q3L; the high-side switch Q5 has ahigh-side terminal Q5H and a low-side terminal Q5L. The high-sideterminal Q1H of the high-side switch Q1, the high-side terminal Q3H ofthe high-side switch Q3, and the high-side terminal Q5H of the high-sideswitch Q5 are respectively connected to the first power terminal 41 a ofthe drive circuit 43.

Optionally, the plurality of low-side switches are switches Q2, Q4, andQ6 in FIG. 5. Each low-side switch also has a high-side terminal and alow-side terminal: the low-side switch Q2 has a high-side terminal Q2Hand a low-side terminal Q2L; the low-side switch Q4 has a high-sideterminal Q4H and a low-side terminal Q4L; the low-side switch Q6 has ahigh-side terminal Q6H and a low-side terminal Q6L. The low-sideterminal Q2L of the low-side switch Q2, the low-side terminal Q4L of thelow-side switch Q4, the low-side terminal Q6L of the low-side switch Q6are respectively connected to the second power terminal 41 b of thedriver circuit 43.

The low-side terminal Q1L of the above-mentioned high-side switch Q1 isconnected to the high-side terminal Q2H of the low-side switch Q3, thelow-side terminal Q3L of the high-side switch Q3 is connected to thehigh-side terminal Q4H of the low-side switch Q4, and the low-sideterminal Q5L of the high-side switch Q5 is connected to the high-sideterminal Q6H of the low-side switch Q6.

In an example, the low-side terminal Q1L of the high-side switch Q1 andthe high-side terminal Q2H of the low-side switch Q2 are both connectedto the first phase winding A; the low-side terminal Q3L of the high-sideswitch Q3 and the high-side terminal Q4H of the low-side switch Q4 areboth connected to the second phase winding B; the low-side terminal Q5Lof the high-side switch Q5 and the high-side terminal Q6H of thelow-side switch Q6 are both connected to the third phase winding C. Thethree-phase windings A, B, and C of the brushless motor 44 are connectedto the power supply module 41 through a bridge composed of the pluralityof high-side switches Q1, Q3, Q5 and the plurality of low-side switchesQ2, Q4, Q5 mentioned above. The above-mentioned high-side switches andlow-side switches may be semiconductor devices, such as, for example, ametal-oxide semiconductor field effect transistor (MOSFET) or aninsulated gate bipolar transistor (IGBT). Each high-side switch andlow-side switch is connected in parallel with a parasitic diode. AH, AL,BH, BL, CH, and CL are the control terminals of high-side switch Q1,low-side switch Q2, high-side switch Q3, low-side switch Q4, high-sideswitch Q5, and low-side switch Q6, respectively.

In the following example of using the MOSFET as a switch, the structureof the drive circuit 43 will be described in detail. The controlterminals AH, AL, BH, BL, CH, CL of the switches Q1-Q6 are electricallyconnected to the controller 42 respectively. For the MOSFET, the controlterminal of each switch is the gate, and each drain or source of theswitches Q1-Q6 is connected to each phase winding of the brushless motor44. Alternatively, the drains of the high-side switches Q1, Q3, and Q5are all connected to the first power terminal 41 a of the power supplymodule 41 through the first drive terminal 43 a, and the sources of thehigh-side switches Q1, Q3, Q5 are respectively connected to the firstphase winding A, the second phase winding B, and the third phase windingC; the drains of the low-side switches Q2, Q4, Q6 are respectivelyconnected to the first phase winding A, the second phase winding B, andthe third phase winding C, and the sources of the low-side switches Q2,Q4, and Q6 are all connected to the second power terminal 41 b of thepower supply module 41 through the second drive terminal 43 b. Theswitches Q1-Q6 change their conduction state according to the controlsignals output by the controller 42 in order to change the voltage stateof the power supply module 41 applied to the windings of the brushlessmotor 11. In this example, the high-side switches Q1, Q3, and Q5 arerespectively used to turn on or off the electrical connection betweenthe first phase winding A, the second phase winding B, the third phasewinding C and the first power terminal 41 a of the power supply module41. The low-side switches Q2, Q4, and Q6 are respectively used to turnon or off the electrical connection between the first phase winding A,the second phase winding B, the third phase winding C and the secondpower terminal 41 b of the power supply module 41.

Optionally, the power tool 10 further includes a position detectionmodule 45, which is connected with the brushless motor 44 and thecontroller 42 for detecting the position of the rotor in the brushlessmotor 44. Specifically, when the rotor rotates into a predeterminedrange, the position detection module 45 is in one signal state, and whenthe rotor rotates out of the predetermined range, the position detectionmodule 45 switches to another signal state. In some examples, theposition detection module 45 includes a position sensor 451 (forexample, a Hall sensor). In other examples, the position detectionmodule 45 does not include a position sensor 451 but determines theposition of the rotor and perform commutation based on backelectromotive force signals.

In this example, the position detection module includes a positionsensor 451, and the position sensor 451 is three Hall sensors. As shownin FIG. 4, three Hall sensors are arranged along the circumferentialdirection of the rotor of the brushless motor 44, and the positioninformation of the rotor detected by the Hall sensors is input to theposition detection module 45. The position detection module 45 convertsthe input position of the rotor into the position information of therotor that can be communicated with the controller 42 through logicprocessing and then input the position information to the controller 42.When the rotor rotates into and out of the predetermined range, thesignal of the Hall sensors varies, and the output signal of the positiondetection module 45 varies accordingly.

When the rotor rotates into the predetermined range, the output signalof the position detection module 45 is defined as 1, and when the rotorrotates out of the predetermined range, the output signal of theposition detection module 45 is defined as 0. The three Hall sensors arearranged at a physical angle of 120° from each other.

When the rotor rotates, the three Hall sensors will generate positionsignals including six signal combinations so that the position detectionmodule 45 outputs a position signal from one of the six signalcombinations. If arranged in the order in which the Hall sensors areplaced, there will be six different signal combinations 100, 110, 010,011, 001, and 101. In this way, the position detection module 45 canoutput one of the six position signals mentioned above, and thus theposition of the rotor can be determined according to the positiondetection signal output by the position detection module 45.

The brushless motor 44 with three-phase windings has six drive states ina power-on period, which corresponds to the output signal generated bythe above solution. Therefore, the brushless motor 44 performscommutation when the output signal from the position detection module 45changes.

In order to make the brushless motor 44 rotate, the drive circuit 43 hasmultiple drive states. In each drive state, the stator windings of thebrushless motor 44 generate a magnetic field. The controller 42 controlsthe drive circuit 43 to switch the drive state to rotate the magneticfield generated by the winding, so as to drive the rotor to rotate, andthereby driving the brushless motor 44.

In order to drive the brushless motor 44, the drive circuit 43 has atleast six drive states. For the convenience of description, hereafter,the drive state is represented by the connection terminals correspondingto the drive state. For example, if the controller 42 controls the drivecircuit 43 to connect the first phase winding A to the first powerterminal 41 a of the power supply module 41 and connect the second phasewinding B to the second power terminal 41 b of the power supply module41, the drive state is represented as AB, and in this state, the firstphase winding A and the second phase winding B are energized, which isreferred to as AB phase conduction. If the controller 42 controls thedrive circuit 43 to connect the first phase winding A to the secondpower terminal 41 b of the power module 41 and connect the second phasewinding B to the first power terminal 41 b of the power module 41, thedrive state is represented as BA, and in this state, the first phasewinding A and the second phase winding B are energized, which isreferred to as BA phase conduction, its current direction being oppositeto that of AB. The drive mode expressed in this way is also applicableto the delta connection scheme of windings. In addition, the switchingof the drive state may also be simply referred to as the commutationoperation of the brushless motor 44. Obviously, the brushless motor 44commutates once per 60° electrical angle rotation by the rotor. Theinterval from one commutation to the next commutation of the brushlessmotor 44 is defined as the commutation interval.

FIG. 6A is a waveform diagram of a first conventional control signal ofthe drive circuit 43. The high-side switches (Q1, Q3, Q5) in a currentcircuitry use pulse width modulation (PWM) signal to control the motorspeed. Specifically, during the PWM signal control period of one of thehigh-side switches, one of the low-side switches maintains a conductingstate, and the high-side switch, the low-side switch and thecorresponding windings form a current circuitry, in which the powersupply current from the power supply module 41 passes through the firstdrive terminal 43 a, the high-side switch, the windings, and thelow-side switch. For example, when the controller 42 controls thebrushless motor 44 to make the motor drive state to be the AB state, thehigh-side switch Q1 is controlled by the PWM signal. During the PWMcontrol period of the high-side switch Q1, the controller 42 outputs alow-level signal to the low-side switch Q4 so as to keep it in theconducting state; the high-side switch Q1, the low-side switch Q4, thecorresponding first phase winding A and second phase winding B form acurrent circuitry, in which the power supply module 41 of the powersupply current from the power supply module 41 passes through the firstdrive terminal 43 a, the high-side switch Q1, the first phase winding A,the second phase winding B, the low-side switch Q4, and the second driveterminal 43 b, as shown in FIG. 7A.

FIG. 6B is a waveform diagram of a second conventional control signal.The low-side switches (Q2, Q4, Q6) in a current circuitry use pulsewidth modulation (PWM) signal to control the motor speed. Specifically,during the PWM signal control period of one of the low-side switches,one of the high-side switches maintains a conducting state, and thehigh-side switch, the low-side switch and the corresponding windingsform a current circuitry, in which the power supply current from thepower supply module 41 passes through the first drive terminal 43 a, thehigh-side switch, the windings, the low-side switch, and the seconddrive terminal. For example, when the controller 42 controls thebrushless motor 44 to make the motor drive state to be the AB state, thelow-side switch Q4 is controlled by the PWM signal. During the PWMsignal control period of the low-side switch Q4, the controller 42outputs a high-level signal to the high-side switch Q1 so as to keep itin the conducting state, the high-side switch Q1, the low-side switchQ4, the corresponding first phase winding A and second phase winding Bform a current circuitry, in which the power supply module 41 of thepower supply current from the power supply module 41 passes through thefirst drive terminal 43 a, the high-side switch Q1, the first phasewinding A, the second phase winding B, the low-side switch Q4, and thesecond drive terminal 43 b.

During the operation of the brushless motor 44, when the rotor rotatesthrough an electrical angle of 60°, the brushless motor 44 commutesonce, that is, every time the rotor rotates through an electrical angleof 60°, the motor drive state is switched from the previous state to thenext state. With reference to FIG. 6A, 7A and 7B, the process in whichthe controller 42 controls the motor drive state of the brushless motor44 to switch from the AB state to the AC state is described as anexample, wherein the high-side switch PWM signal control method isadopted: the controller 42 outputs a PWM signal to the control terminalAH of the high-side switch Q1 to turn on or off the high-side switch Q1,and the controller 42 synchronously outputs a high-level signal to thecontrol terminal BL of the low-side switch Q4 to keep the low-sideswitch Q4 in the conducting state, the first phase winding A and thesecond phase winding B are energized, and the motor drive state is inthe AB state (as shown in FIG. 7A); the controller 42 outputs a PWMsignal to the control terminal AH of the high-side switch Q1 to turn onor off the high-side switch Q1, and the controller 42 synchronouslyoutputs a low-level signal to the control terminal BL of the low-sideswitch Q4 to keep the low-side switch Q4 off, and the controller 42synchronously outputs a high-level signal to the control terminal CL ofthe low-side switch Q6 to keep the low-side switch Q6 in the conductingstate, the motor drive state is switched from the AB state to the ACstate, the first phase winding A and the third phase winding C areenergized, and the second phase winding B is de-energized (as shown inFIG. 7B).

However, because each switch has a parasitic diode connected inparallel, during the PWM signal control period of one of the high-sideswitches, when it switches from the on state to the off state, due tothe existence of inductive elements in the circuitry (for example, thewindings of the motor), the current is not transient, and the motorcurrent will pass through the parasitic diode of the low-side switchconnected to the low-side terminal of the high-side switch. As shown inFIG. 7A, when the motor drive state is in the AB state, the high-sideswitch Q1 is turned on and the low-side switch Q4 is turned on, when themotor drive state is switched from the AB state as shown in FIG. 7A tothe AC state as shown in FIG. 7B, due to the existence of inductiveelements, as shown in FIG. 8, the current is not transient. For example,when the high-side switch is controlled with the PWM, the non-transientcurrent will pass through the parasitic diode in parallel with thehigh-side switch Q3. The parasitic diode of the high-side switch Q3generates heat from internal resistance, and the temperature of thehigh-side switch Q3 and the drive circuit 43 connected in parallel withthe parasitic diode rises. Specifically, under heavy load and highcurrent, the heating loss is more severe. Therefore, this traditionalcontrol method will bring relatively severe power loss.

In order to overcome the above technical problem, the heat generationproblem caused by the current passing through the parasitic diode,referring to FIG. 9, the controller 42 of the power tool 10 of thepresent disclosure is configured to: output a first control signal toone of the high-side switches (Q1, Q3, Q5) to make one of the high-sideswitches (Q1, Q3, Q5) in an on state or an off state; output a secondcontrol signal to one of the low-side switches (Q2, Q4, Q6) to make oneof the low-side switches (Q2, Q4, Q6) in the other of the on state andthe off state; wherein, the low-side terminal of one of the high-sideswitches (Q1, Q3, Q5) is connected to the high-side terminal of one ofthe low-side switches (Q2, Q4, Q6) to reduce heat generation and powerloss. In other words, in this example, when the first control signalcauses one of the high-side switches to be in the off state, the secondcontrol signal causes the low-side switch directly connected to thelow-side terminal of the high-side switch to be in the on state; and/or,when the second control signal causes one of the low-side switches to bein the off state, the first control signal causes the high-side switchdirectly connected to the high-side terminal of the low-side switch tobe in the on state. In other words, in this example, the high-sideswitch and the low-side switch in which the low-side terminal of thehigh-side switch and the high-side terminal of the low-side switch aredirectly connected have opposite on-off states. The advantage of thissolution is to make the non-transient current pass through the high-sideswitch directly connected to the high-side terminal of the low-sideswitch or pass through the low-side switch directly connected to thelow-side terminal of the high-side switch instead of passing through theparasitic diode to reduce heat generation and power loss.

Further, the first control signal output by the controller 42 is a firstPWM signal and the second control signal output by the controller 42 isa second PWM signal.

Alternatively, the controller synchronously outputs the first controlsignal and the second control signal.

According to a specific example, the high-side switch adopts a PWMsignal control method, and the controller 42 is configured to: output afirst control signal to make one of the high-side switches in an onstate or an off state, and the first control signal is the first PWMsignal; output a high-level signal to keep one of the low-side switchesin the on state during the PWM signal control period of the high-sideswitch to form a current circuitry; synchronously output a secondcontrol signal to make the low-side switch connected to the low-sideterminal of the high-side switch in the other of the on state and theoff state, and the second control signal is the second PWM signal.Taking the motor drive state in the AB state as an example, thecontroller 42 outputs a first control signal to make the high-sideswitch Q1 in an on state or an off state, the first control signal isthe first PWM signal, and the controller 42 outputs a high-level signalto keep the low-side switch Q4 in the on state during the PWM signalcontrol period of the high-side switch Q1 to form a current circuitry;the controller 42 synchronously outputs the second control signal tomake the low-side switch Q2 connected to the low-side terminal of thehigh-side switch Q1 in the other of the on state and the off state, andthe second control signal is the second PWM signal.

According to another specific example, the low-side switch adopts a PWMsignal control method, and the controller 42 is configured to: output asecond control signal to make one of the low-side switches in an onstate or an off state, and the second control signal is the second PWMsignal; output a high-level signal to keep one of the high-side switchesin the on state during the PWM signal control period of the low-sideswitch to form a current circuitry; synchronously output a first controlsignal to make the high-side switch connected to the high-side terminalof the low-side switch in the other of the on state and the off state,and the first control signal is the first PWM signal. Taking the motordrive state in the AB state as an example, the controller 42 outputs asecond control signal to make the low-side switch Q4 in an on state oran off state, the second control signal is the second PWM signal, andthe controller 42 outputs a high-level signal to keep the high-sideswitch Q1 in the on state during the PWM signal control period of thelow-side switch Q4 to form a current circuitry; the controller 42synchronously outputs the first control signal to make the high-sideswitch Q3 connected to the high-side terminal of the low-side switch Q4in the other of the on state and the off state, and the first controlsignal is the first PWM signal.

The foregoing description is only illustrative and does not limit thecontent of the present disclosure. It should be understood that otherphases similarly follows to the foregoing example, and will not berepeated herein.

Referring to FIG. 10, as an alternative, only when the duty cycle of thefirst PWM signal meets certain preset conditions does the controller 42output the second PWM signal synchronously. Specifically, only when theduty cycle of the first PWM signal falls within the predetermined rangedoes the controller 42 output the second PWM signal.

Optionally, at least when the duty cycle of the first PWM signal is inthe range of 20% to 90% (including 20% and 90%) does the controller 42output the second PWM signal.

Optionally, at least when the duty cycle of the first PWM signal is inthe range of 10% to 95% (including 10% and 95%) does the controller 42output the second PWM signal to control the low-side switch of the phasebridge circuit.

Optionally, at least when the duty cycle of the first PWM signal is inthe range of 30% to 95% (including 30% and 95%) does the controller 42output the second PWM signal to control the low-side switch of the phasebridge circuit.

In this way, only when the duty cycle of the first PWM signal meets thepreset conditions does the controller 42 output the second PWM signal.The advantages are as follows: on the one hand, when the first PWMsignal output by the controller 42 makes one of the high-side switchesto be in the off state, the second PWM signal output by the controller42 makes the low-side switch connected to the low-side terminal of thehigh-side switch to be in the on state. If the duty cycle of the firstPWM signal is small, the current of the corresponding winding drops fastsuch that the current is prone to be less than zero. A current less thanzero will produce a negative torque and cause a brake effect to reducethe motor speed, which is disadvantageous, and if the low-side switchconnected to the low-side terminal of the high-side switch is turned onwhen the high-side switch is turned off, this disadvantage will beaggravated. Plus, when the duty cycle of the first PWM signal is small,the current flowing through the high-side switch is small, so the heatgenerated is small, and at this time, the controller 42 does not need tooutput the second PWM signal to control the low-side switch connected tothe low-side terminal of the high-side switch to reduce heat generationand power loss. On the other hand, when the first PWM signal output bythe controller 42 makes one of the high-side switches to be in the offstate, the second PWM signal output by the controller 42 makes thelow-side switch connected to the low-side terminal of the high-sideswitch to be in the on state. If the duty cycle of the first PWM signalis large, the above scheme will make the duty cycle in which the secondPWM signal could be inserted to be very small, yielding little effect,and on the contrary, causing switching loss due to frequent switching ofthe switches.

Referring to FIG. 11, in an example, there is a first preset duration T1between the falling edge of the first control signal and the rising edgeof the second control signal, and there is a second preset duration T2between the rising edge of the first control signal and the falling edgeof the second control signal. In other words, the first preset durationT1 is the time interval between the falling edge of the first controlsignal and the rising edge of the second control signal, and the secondpreset duration T2 is the time interval between the rising edge of thefirst control signal and the falling edge of the second control signal.

The advantages are as follows: on the one hand, it avoids the situationthat when the first control signal is at the falling edge, the risingedge of the second control signal starts immediately, and the low-sideswitch has been turned on when the high-side switch has not beencompletely turned off, which may cause a short-circuit, and therebyburning the circuit and electronic components. In particular, referringto FIG. 12A, due to rise/fall times, the actual square wave signals arenot perfect squares, its rising and falling edges are not transient, butrather shows a slow variation with a small delay time T. Referring toFIG. 12B, taking phase A as an example, when the first control signaloutput by the controller 42 turns off the high-side switch Q1, thesecond control signal output by the controller 42 turns on the low-sideswitch Q2 connected to the low-side terminal of the high-side switch Q1.If the rising edge of the second control signal starts immediately whenthe first control signal is at the falling edge, the high-side switch Q1and the low-side switch Q2 may be turned on at the same time. Theoccurrence of short-circuit phenomenon may easily damage or even burnthe electronic components. By adopting the first preset duration T1between the falling edge of the first control signal and the rising edgeof the second control signal, the occurrence of the above-mentionedshort-circuit phenomenon can be effectively avoided.

On the other hand, it avoids the generation of negative torque and thebrake effect. Specifically, referring to FIGS. 13A and 13B, taking phaseA as an example, during the PWM control period, if the load is large andthe current I1 of the first phase winding A is large, the motor willcontinue to output forward torque; if the load is small and the currentI2 of the first phase winding A is small, the first control signaloutput by the controller 42 causes the high-side switch Q1 to be in theoff state, and the second control signal output by the controller 42causes the low-side switch Q2 connected to the high-side switch Q1 to bein the on state, if the low-side switch Q2 remains on for a long time,the current I1 will drop fast, maybe to a negative value; at this time,a negative torque 131 will be generated, resulting in the brake effectthat decreases the motor speed.

Similarly, when the low-side switches realizes the PWM control method,as an option, the value range of the duty cycle of the second PWM signalis 20% to 90%. Optionally, the value range of the duty cycle of thesecond PWM signal is 10% to 95%. Optionally, the value range of the dutycycle of the second PWM signal is 30% to 95%.

By adopting the second preset time period T2 between the rising edge ofthe first control signal and the falling edge of the second controlsignal, the generation of negative torque and the decrease of the motorspeed can be effectively avoided. Specifically, referring to FIG. 13C,taking phase A as an example, the first control signal output by thecontroller 42 is applied to the control terminal AH of the high-sideswitch Q1, and the second control signal output by the controller 42 isapplied to the control terminal AL of the low-side switch Q2 connectedto the low-side terminal of the high-side switch Q1. After each fallingedge of the first control signal starts, wait for the first presetduration T1 to start the rising edge of the second control signal, andafter the falling edge of the second control signal starts, wait for thesecond preset duration T2 to start the rising edge of the first controlsignal. Wherein, the first control signal is the first PWM signal, andthe second control signal is the second PWM signal. Due to the existenceof the first preset duration T1 and the second preset duration T2, thesituation that both the high-side switch Q1 and the low-side switch Q2are turned on at the same time will not occur, thereby avoiding theoccurrence of the short-circuit phenomenon, and under light loadconditions, the existence of the second preset duration T2 can avoid theoccurrence of negative torque, which causes the brake effect and reducesthe motor speed.

Optionally, the value range of the first preset duration T1 is 0.5microseconds to 10 microseconds (including the endpoints 0.5microseconds and 10 microseconds). Optionally, the value range of thesecond preset duration is 5 microseconds to 30 microseconds.

Actual experimental results show that when the first preset duration T1is between 0.5 microseconds and 10 microseconds (including the endpoints0.5 microseconds and 10 microseconds), the short circuit problem couldbe prevented, and the suppression of temperature rise is more effective.

In an example, only utilise the first preset duration T1 between thefalling edge of the first control signal and the rising edge of thesecond control signal, so as to avoid the high-side switch and thelow-side switch connected to the low-side terminal of the high-sideswitch from being turned on at the same time, which causes a shortcircuit. In an example, only utilise the second preset duration T2between the rising edge of the first control signal and the falling edgeof the second control signal, so as to avoid the generation of negativetorque that causes the brake effect. The above two examples are similarto the first example and will not be repeated herein.

Alternatively, the sum of the duty cycle of the first PWM signal and theduty cycle of the second PWM signal may be configured to be less than100% to avoid the high-side switch and the low-side switch connected tothe low-side terminal of the high-side switch from being turned on atthe same time, which causes a short circuit, and/or avoid the generationof negative torque that causes the brake effect and reduces the motorspeed.

For the drive circuit 43, when the high-side switch is in the on stateand the low-side switch connected to the low-side terminal of thehigh-side switch is in the off state, the current corresponding to theconducting windings rises. Conversely, when the high-side switch is inthe off state and the low-side switch connected to the low-side end ofthe high-side switch is in the on state, the current corresponding tothe conducting windings drops.

In order to control the motor of the power tool to keep outputtingpositive torque to suppress the brake effect caused by negative torquegenerated when the motor is driven, the ratio of the first presetduration T1 and the second preset duration T2 should be less than orequal to 1. In a specific example, for example, the first presetduration T1 is set to 0.5 microseconds, and the second preset durationT2 is set to 0.8 microseconds; for another example, the first presetduration T1 is set to 1 microsecond, and the second preset duration T2is set to 2 microsecond; for another example, the first preset durationT1 is set to 10 microseconds, and the second preset duration T2 is setto 13 microseconds. The foregoing description is only illustrative andis not a limitation of the present disclosure.

On this basis, the second preset duration T2 is dynamically adjusted sothat the current of the motor winding is greater than or equal to zero.In this way, the motor does not output negative torque, which generatesthe brake effect to reduce the motor speed when the motor is driven.

Optionally, the power tool 10 further includes a current measuringmodule 46 (FIG. 4) for detecting or estimating the phase current.

In the high-side switch PWM signal control mode, the controller 42 isconfigured to: when the phase current is less than or equal to zero, thecontroller 42 outputs the second control signal to turn off one of thelow-side switches, so that the motor keeps outputting positive torque,one of the low-side switches is the low-side switch connected to thelow-side terminal of the high-side switch that is currently on.

In the low-side switch PWM signal control mode, the controller 42 isconfigured to: when the phase current is less than or equal to zero, thecontroller 42 outputs the first control signal to turn off one of thehigh-side switches, so that the motor keeps outputting positive torque,one of the high-side switches is the high-side switch connected to thehigh-side terminal of the low-side switch that is currently on.

During the drive process of the motor, in order to prevent thetemperature of the switches (Q1-Q6) from being too high and damaging theelectronic components, it is necessary to sample the temperature of oneor more switches (Q1-Q6) in order to monitor the temperature. In thetraditional method, an NTC temperature sensor for temperature samplingis generally arranged on the circuit board near at least one switch ofthe drive circuit to effectively monitor the temperature of the bridgeswitches and prevent damage to the electronic components due toexcessive temperature. However, the additional temperature sensor willnot only increase the design and component cost of the circuit board,but also increase the size of the circuit board.

Alternatively, in order to overcome the above-mentioned problems, thecontroller 42 of the present disclosure adopts an MCU integrated with atemperature sensor and uses this temperature sensor to replace theadditional temperature sampling NTC temperature sensor to estimate thetemperature of the switches of the drive circuit 43. When the detectedtemperature value of the drive circuit 43 exceeds a predeterminedthreshold, the controller 42 controls the drive circuit 43 to stopworking. Using the temperature sensor integrated inside the controller42 to measure the temperature of the drive circuit 43 can simplify thecircuit board design, save parts cost, and make the circuit board morecompact. In some specific examples, the sum of the single-sided area ofthe circuit board is less than 2500 cm{circumflex over ( )}2.

In some specific examples, a single-chip microcomputer is provided witha temperature sensor integrated therein, which can be used to measurethe temperature surrounding the CPU. The measured result can be used toestimate the temperature of the drive circuit 43. When the detectedtemperature exceeds a predetermined value, activate the temperatureprotection mechanism, for example, turned off the power tool, turn onthe cooling fan, and shut the drive circuit 43.

The above example is based on the power tool 10 with the brushless motor44 with three-phase windings. Those skilled in the art should understandthat the above technical solution could also be applied to other powertools with a brushless motor 44, such as two-phase brushless motor.

The present disclosure also discloses a control method of a power tool.The power tool includes a drive circuit and the drive circuit includes:a first drive terminal electrically connected to the first powerterminal; a second drive terminal electrically connected to the secondpower terminal; a plurality of high-side switches, each high-side switchhaving a high-side terminal and a low-side terminal, the high-sideterminals of the plurality of high-side switches being respectivelyelectrically connected to the first drive terminal; a plurality oflow-side switches, each low-side switches having a high-side terminaland a low-side terminal, the low-side terminals of the plurality oflow-side switches being respectively electrically connected to thesecond drive terminal. The control method of the power tool comprises:making one of the plurality of high-side switches in an on state or anoff state; making one of the plurality of low-side switches in the otherof the on state and off state; wherein the low-side terminal of one ofthe plurality of high-side switches is connected to the high-sideterminal of one of the plurality of low-side switches, so that thenon-transient current flows through the low-side switch instead of theparasitic diode connected in parallel with the low-side switch to reduceheat generation and power loss.

Optionally, the first control signal is a first PWM signal and thesecond control signal is a second PWM signal.

Optionally, the controller outputs the second control signal only whenthe first control signal meets a preset condition. The advantages are asfollows: on the one hand, when the duty cycle of the first PWM signal issmall, it can avoid aggravating the generation of negative torque, andunnecessary switching of the low-side switch connected to the low-sideterminal of the high-side switch; on the other hand, when the duty cycleof the first PWM signal is large, it can avoid switching of the low-sideswitch connected to the low-side terminal of the high-side switch, suchthat switching loss caused by frequent switching of the switch could beavoided.

Optionally, the value range of the duty cycle of the first PWM signal is20% to 90%.

Optionally, the value range of the duty cycle of the first PWM signal is10% to 95%.

Optionally, the value range of the duty cycle of the first PWM signal is30% to 95%.

Optionally, there is a first preset duration T1 between the falling edgeof the first control signal and the rising edge of the second controlsignal. The advantage of this is that it can avoid the situation thatwhen the high-side switch is turned on, the low-side switch connected tothe low-side terminal of the high-side switch is turned onsimultaneously, which may cause a short circuit.

Optionally, the first preset duration T1 has a value range of 5microseconds to 10 microseconds, (including the endpoints), which canprevent the short-circuit problem and suppress temperature rise.

Optionally, there is a second preset duration T2 between the rising edgeof the first control signal and the falling edge of the second controlsignal. The advantage of this is that it can avoid the generation ofnegative torque that causes the brake effect to reduce the motor speed.

Optionally, there is a first preset period of time T1 between thefalling edge of the first control signal and the rising edge of thesecond control signal, and there is a second preset duration T2 betweenthe rising edge of the first control signal and the falling edge of thesecond control signal. The advantage of this is that it can avoid theshort-circuit problem and suppress the temperature rise and avoid thenegative torque that causes the brake effect to reduce the motor speed.

Optionally, the ratio of the first preset duration T1 to the secondpreset duration T2 is less than or equal to 1. The advantage of this isthat it can further avoid the generation of negative torque that causesthe brake effect to reduce the motor speed.

Optionally, the sum of the duty cycle of the first PWM signal and theduty cycle of the second PWM signal is less than 100%. The advantage ofthis is that it can prevent the short circuit problem while suppressingthe temperature rise and/or can avoid the generation of negative torquethat causes the brake effect to reduce the motor speed.

Optionally, the control method of the power tool further includes: whenthe phase current is less than or equal to zero, outputting a secondcontrol signal to turn off one of the low-side switches, so that themotor keeps outputting positive torque. Said one of the low-sideswitches is the low-side switch connected to the low-side terminal ofthe high-side switch that is currently on.

The above-mentioned examples are based on the example that the high-sideswitches adopt the PWM control method. For the low-side switchesadopting the PWM control method, the control method is similar to theabove-mentioned examples, and will not be repeated herein.

It should be noted that, for the low-side switch adopting the PWMcontrol method, optionally, the value range of the duty cycle of thesecond PWM signal is 20% to 90%. Optionally, the value range of the dutycycle of the second PWM signal is 10% to 95%. Optionally, the valuerange of the duty cycle of the second PWM signal is 30% to 95%.

The basic principles, main features and advantages of the presentdisclosure have been shown and described above. Those skilled in the artshould understand that the above-mentioned examples do not limit thepresent disclosure in any form, and all technical solutions obtained byequivalent substitutions or equivalent transformations fall within theprotection scope of the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure provides a power tool and a control method, whichcan effectively suppress the temperature rise of the drive circuit andreduce power loss.

What is claimed is:
 1. A power tool, comprising: a functional componentfor realizing a function of the power tool; a motor for driving thefunctional component, the motor having a plurality of windings; a powersupply module configured to provide a power supply current, the powersupply module comprising a first power terminal and a second powerterminal; a drive circuit electrically connected to the motor, the drivecircuit comprising: a first drive terminal electrically connected withthe first power terminal; a second drive terminal electrically connectedwith the second power terminal; a plurality of high-side switcheswherein high-side terminals of the plurality of high-side switches arerespectively electrically connected to the first drive terminal; aplurality of low-side switches wherein low-side terminals of theplurality of low-side switches are respectively electrically connectedto the second drive terminal; a current measuring module configured todetect or estimate phase current; and a controller configured to: outputa first control signal to a one of the plurality of high-side switchesto place the one of the plurality of high-side switches in an on stateor an off state; and output a second control signal to a one of theplurality of low-side switches to place the one of the plurality oflow-side switches in the other of the on state and the off state;wherein the low-side terminal of the one of the plurality of high-sideswitches is connected to the high-side terminal of the one of theplurality of low-side switches and the controller is configured tooutput the second control signal to turn off the one of the plurality oflow-side switches or output the first control signal to turn off the oneof the plurality of high-side switches when the phase current is lessthan or equal to zero.
 2. The power tool of claim 1, wherein the firstcontrol signal output by the controller is a first PWM signal and thesecond control signal output by the controller is a second PWM signal.3. The power tool of claim 2, wherein a duty cycle of the first PWMsignal ranges from 10% to 95%.
 4. The power tool of claim 1, wherein aninterval between a falling edge of the first control signal and a risingedge of the second control signal is a first preset duration and thefirst preset duration ranges from 5 microseconds to 10 microseconds. 5.The power tool of claim 1, wherein an interval between a rising edge ofthe first control signal and a falling edge of the second control signalis a second preset duration.
 6. The power tool of claim 5, wherein thesecond preset duration ranges from 5 microseconds to 30 microseconds. 7.The power tool of claim 1, wherein an interval between a falling edge ofthe first control signal and a rising edge of the second control signalis a first preset duration and an interval between a rising edge of thefirst control signal and a falling edge of the second control signal isa second preset duration.
 8. The power tool of claim 7, wherein a ratioof the first preset duration to the second preset duration is less thanor equal to
 1. 9. The power tool of claim 1, wherein the controlleroutputs the first control signal and the second control signalsynchronously.
 10. The power tool of claim 2, wherein a sum of a dutycycle of the first PWM signal and a duty cycle of the second PWM signalis less than 100%.
 11. The power tool of claim 2, wherein a duty cycleof the second PWM signal ranges from 10% to 95%.
 12. The power tool ofclaim 1, wherein the controller comprises a temperature sensor arrangedinside the controller, the controller estimates a temperature of thedrive circuit according to a detection value of the temperature sensor,and,when the detection value of the temperature of the drive circuitexceeds a predetermined threshold, the controller controls the drivecircuit to stop working.
 13. A power tool, comprising: a functionalcomponent for realizing a function of the power tool; a motor fordriving the functional component, the motor having a plurality ofwindings; a power supply module configured to provide a power supplycurrent, the power supply module comprising a first power terminal and asecond power terminal; a drive circuit electrically connected to themotor, the drive circuit comprising: a first drive terminal electricallyconnected with the first power terminal; a second drive terminalelectrically connected with the second power terminal; a first high-sideswitch wherein a high-side terminal of the first high-side switch iselectrically connected to the first drive terminal; a first low-sideswitch wherein a low-side terminal of the first low-side switch iselectrically connected to the second drive terminal; a current measuringmodule configured to detect or estimate phase current; and a controllerconfigured to: output a first control signal to the first high-sideswitch to place the first high-side switch in an on state or an offstate; and output a second control signal to the first low-side switchto place the first low-side switch in the other of the on state and theoff state; wherein the low-side terminal of the first high-side switchis connected to the high-side terminal of the first low-side switch andthe controller is configured to output the second control signal to turnoff the first low-side switches or output the first control signal toturn off the first high-side switches when the phase current is lessthan or equal to zero.
 14. The power tool of claim 13, wherein the firstcontrol signal output by the controller is a first PWM signal and thesecond control signal output by the controller is a second PWM signal.15. The power tool of claim 14, wherein a duty cycle of the first PWMsignal ranges from 10% to 95%.
 16. The power tool of claim 13, whereinan interval between a falling edge of the first control signal and arising edge of the second control signal is a first preset duration andan interval between a rising edge of the first control signal and afalling edge of the second control signal is a second preset duration.17. A power tool, comprising: a functional component for realizing afunction of the power tool; a motor for driving the functionalcomponent, the motor having a plurality of windings; a power supplymodule configured to provide a power supply current, the power supplymodule comprising a first power terminal and a second power terminal; adrive circuit electrically connected to the motor, the drive circuitcomprising: a first drive terminal electrically connected with the firstpower terminal; a second drive terminal electrically connected with thesecond power terminal; a first high-side switch wherein a high-sideterminal of the first high-side switch is electrically connected to thefirst drive terminal; a first low-side switch wherein a low-sideterminal of the first low-side switch is electrically connected to thesecond drive terminal; and a controller configured to: output a firstcontrol signal to the first high-side switch to place the firsthigh-side switch in an on state or an off state; and output a secondcontrol signal to the first low-side switch to place the first low-sideswitch in the other of the on state and the off state; wherein thelow-side terminal of the first high-side switch is connected to thehigh-side terminal of the first low-side switch and an interval betweena rising edge of the first control signal and a falling edge of thesecond control signal is a second preset duration.
 18. The power tool ofclaim 17, wherein the first control signal output by the controller is afirst PWM signal and the second control signal output by the controlleris a second PWM signal.
 19. The power tool of claim 18, wherein a dutycycle of the first PWM signal ranges from 10% to 95%.
 20. The power toolof claim 17, wherein the second preset duration ranges from 5microseconds to 30 microseconds.